1. Field of the Invention
In internal combustion engines, fuel injectors are used, with which fuel that is at high pressure is injected into the combustion chambers of the engine. Such fuel injectors, which are used for instance in self-igniting internal combustion engines, include an injector housing, which is in communication with a high-pressure source located outside the fuel injector, such as a high-pressure collection chamber (common rail). The high-pressure collection chamber is supplied in turn with fuel that is at high pressure via a high-pressure pump.
2. Prior Art
German Patent Disclosure 10 2004 037 125.3 relates to a common rail injector including an injector housing with a fuel inlet, which is in communication with a central high-pressure fuel source outside the injector housing and with a pressure chamber inside the injector housing. From the latter, as a function of the pressure in a nozzle needle control chamber, fuel subjected to high pressure is injected into a combustion chamber of an internal combustion engine when a nozzle needle lifts from its seat. The nozzle needle control chamber is in communication with an actuator pressure chamber that is defined by an actuator, which is preferably a piezoelectric actuator. Between the actuator pressure chamber and the nozzle needle control chamber, a throttle device is disposed, which upon evacuation of the nozzle needle control chamber makes possible a smaller flow rate from the nozzle needle control chamber into the actuator pressure chamber than upon filling of the nozzle needle control chamber from the actuator pressure chamber into the nozzle needle control chamber. The throttle device is designed and disposed such that it develops its throttling action only upon evacuation of the nozzle needle control chamber, while upon filling of the nozzle needle control chamber it does not develop any throttling action but instead assures an unhindered flow through of fuel. The throttle device includes a throttle piston, which has a through hole that makes a throttled flow through of fuel from the nozzle needle control chamber into the actuator pressure chamber possible.
In fuel injectors in which the pressure in a control chamber is controlled by an actuator, such as a piezoelectric actuator, the term used is also direct control, or in other words a direct control of the injection valve member, which for example may be embodied as a nozzle needle.